Glioblastoma (GBM) of the internal auditory canal (IAC) is exceedingly rare, with only 3 prior cases reported in the literature. The authors present the fourth case of cerebellopontine angle (CPA) and IAC GBM, and the first in which the lesion mimicked a vestibular schwannoma (VS) early in its natural history. A 55-year-old man presented with tinnitus, hearing loss, and imbalance. MRI identified a left IAC/CPA lesion measuring 8 mm, most consistent with a benign VS. Over the subsequent 4 months he developed facial weakness. The tumor grew remarkably to 24 mm and surgery was recommended; the main preoperative diagnosis was malignant peripheral nerve sheath tumor (MPNST). Resection proceeded via a translabyrinthine approach with resection of cranial nerves VII and VIII, followed by facial-hypoglossal nerve anastomosis. Intraoperative frozen section suggested malignant spindle cell neoplasm, but final histopathological and molecular testing confirmed the lesion to be a GBM. The authors report the first case in which absence of any brainstem interface effectively excluded a primary parenchymal tumor, in particular GBM, from the differential diagnosis. Given the dramatic differences in treatment and prognoses between malignant glioma and MPNST, this case emphasizes the importance of surgical intervention on an aggressively growing lesion, which provides both the best probability of local control and the critical tissue diagnosis.

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Background Chronic tinnitus affects millions of people globally and constitutes the most commonly compensated disability among military service members in the United States. Existing treatment options largely surround helping patients cope with their disease as opposed to directly suppressing tinnitus perception. The current study investigated the efficacy of electrical stimulation of the cochlea on chronic disabling tinnitus. Methods In this single-arm, open-label clinical trial, 22 adult subjects with severe-range asymmetric or unilateral non-pulsatile tinnitus underwent electrical stimulation of the cochlea through use of an extra-cochlear electrode positioned on the cochlear promontory. Each subject underwent 3 stimulation treatments over 3 weeks at 7-day intervals. Tinnitus severity was determined by Tinnitus Handicap Inventory (THI), Tinnitus Functional Index (TFI), and Tinnitus Visual Analog Scale (VAS). Inclusion criteria required subjects have no worse than moderate sensorineural hearing loss determined by pre-enrollment audiometric testing. The primary outcome was nadir post-treatment THI scores, obtained at seven timepoints following electrical stimulation, with clinically significant improvement defined as a decrease of  ≥ 7. Results All 22 (100%) subjects experienced clinically significant improvement in the THI during the study period with a mean decrease in scores of − 31 (95% CI − 38 to − 25) from a baseline of 48. Twenty (91%) experienced clinically significant improvement detectable on at least two of the three tinnitus survey instruments and 17 (77%) experienced clinically significant improvement detectable on all three survey instruments (i.e., THI, TFI, and VAS). Eight (36%) subjects reported either complete (THI of 0; n  = 3) or near-complete (THI 1–4; n  = 5) suppression of their tinnitus following a stimulation session. Thirteen (59%) subjects reported a nadir following stimulation at or below the threshold for “no or slight handicap” on the THI (≤ 16). No adverse events were observed. Conclusions These findings establish the foundation for the development of an extra-cochlear implantable device that delivers electrical stimulation to the cochlea for the treatment of disabling tinnitus. For patients considering device implantation, trans-tympanic cochlear promontory stimulation can facilitate patient selection. Trial Registration ClinicalTrials.gov Identifier: NCT03759834. URL: https://clinicaltrials.gov/ct2/show/NCT03759834

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